In continuous fabric finishing equipment strips of fabric are interconnected by seams, and as the fabric is processed the operator must be alert to the presence of a seam to avoid the seam adversely affecting the processing equipment.
For instance, in a common continuous finishing process of fabric drums and shoes are utilized to stress or compact the fabric. As the movement of a seam through the drums and shoes substantially increases the wear thereon it is common practice to "drop" the shoe as the seam moves through the drums in order to avoid the wear, and possible repair, that results from seam compression. With present fabric speeds the manual detection of seams is difficult, and high wear and maintenance costs are experienced in continuous finishing apparatus due to the inability of the operator to always detect a seam and modify the finishing equipment accordingly.
Fabric finishing equipment may also require that seams be removed from processed strips, and in seam removal apparatus of this type it has been necessary to manually detect the seam, and manually control the apparatus to properly locate the seam relative to the cutting apparatus, and such manual processing is expensive and time consuming.
Heretofore, difficulty has been encountered in the development of automatic seam detection and fabric control apparatus in that the rate of movement of the fabric in continuous fabric finishing apparatus varies greatly in dependence upon the nature of the processing, the fabric, the width of the fabric being processed, and other factors. While seam detection, and subsequent control of processing equipment, may be readily accomplished if the fabric movement is uniform, such variable velocities of fabric strip movement have previously thwarted the successful detection of seams and the subsequent control of processing apparatus.
It is an object of the invention to provide apparatus for detecting the presence of a seam in a strip of rapidly moving fabric, determining the rate of movement of the fabric, and controlling fabric processing equipment in accordance with the seam position relative thereto.
Another object of the invention is to provide apparatus for detecting the presence of a seam in rapidly moving fabric wherein subsequent processing apparatus located at a plurality of variable spaced positions may be timely actuated to accomodate the presence of the seam.
Yet a further object of the invention is to provide a detector for the presence of a seam in a rapidly moving fabric which is of an optical nature utilizing light reflected from the fabric, and wherein the light reflecting characteristics of the fabric are automatically compensated wherein uniform operation is achieved over a wide variety of fabric colors, and even patterns.
Another object of the invention is to provide a seam detection and control apparatus for rapidly moving fabric wherein false or "multiple" initiation of the control system due to inconsistencies in seam configuration are minimized.
In the practice of the invention a detector is located adjacent a rapidly moving web of fabric consisting of a plurality of fabric strips periodically sewn or otherwise affixed together defining a seam, and "behind" the detector with respect to the direction of fabric movement, fabric processing equipment is located which can be adversely affected by the seams and modification thereto is desired upon the seam arriving at such processing equipment. For instance, the fabric may be processed by drums and pressing shoes which stress or compact the fabric as it passes therebetween, and the passing of a seam between the drum and shoe imposes excessive wear thereon.
The detection of a seam is accomplished by an optical sensor wherein light cast upon the fabric face at the detector is reflected into a pair of sensors spaced with respect to each other in the direction of fabric movement. Thus, upon a seam passing under the detector an increased amount of light will be sequentially reflected unto the electronic light sensitive sensors producing two spaced electric signals wherein the duration between the signals represents the rate of movement of the seam, and fabric.
An automatic background control threshold voltage is imposed upon the circuit as determined by an optical sensor located at the detector receiving reflected light, and this threshold voltage is proportional to the reflectivity of the fabric, and modifies the circuit in accordance with the ability of the fabric to reflect light. This automatic background control assures uniform sensitivity and consistent operation with various fabric colors, and will also compensate for many colored patterns.
The spaced electronic signals produced by the detection of the seam initiate several electronic timers. The initial signal initiates the operation of a binary counter while the second signal terminates the counting thereof. Through a converter an analog voltage is produced inversely proportional to the velocity of the fabric movement. Further, the seam produced signal also initiates timing apparatus in the form of a ramp generator, and upon the ramp voltage equaling that produced by the binary counter a relay is tripped which controls the fabric processing equipment. For instance, the relay may actuate a valve mechanism for "dropping" a shoe away from a compressing drum in order to permit the seam to pass therethrough.
In the disclosed circuit two fabric processing stations are disclosed, and another timing circuit is initiated by the ramp generator circuit, which is also of the ramp generator type, wherein a second relay is actuated at a predetermined duration after the first relay whereby the shoe of the second compacting drum may be dropped.
As irregular seams may produce a plurality of signals due to variations in the light reflected thereby the circuit includes means for preventing multiple "start" signals from being imposed upon the circuit, and blanking means are incorporated into the circuit to provide uniform sensing and reduce the likelihood of improper circuit operation.
The seam detection and control system of the invention will detect seams in material traveling up to 250 yards per minute, there is no physical contact with the material, and the apparatus will properly function with both wet and dry fabric. Both overlapping and butt seams can be dependably sensed, and as the operation of the circuit is automatic, damage to fabric processing apparatus due to seams, as occurs with manual inspection, is eliminated.